jobq-wire: name every outcome, keep the enum spellings, document the schema

Three things, all from review:

Accepted outcomes were built from a hand-listed [Done, Failed, Cancelled,
Skipped] array. Exhaustive today, silently short the day someone adds a
variant — the new outcome would vanish from every edge that accepts it.
BitFlags::ALL asks the type instead.

TerminalState carried rename_all = "snake_case" while its sibling State did
not, so one enum shipped "done" and the other "Done". A rename is a second
spelling of a name that then has to be kept in agreement by hand; both now
serialise their variant names verbatim. Nothing else reads TerminalState off
a wire, so no consumer moves. GraphDep's tag values likewise.

The endpoint documented its body as serde_json::Value, which tells a spec
reader nothing. hive-jobq-wire now derives ToSchema. State and TerminalState
are foreign types here and utoipa stays out of the scheduler crate, so the
schema points at local mirror enums. A mirror that drifts is worse than none:
the conversions are exhaustive (a new upstream variant fails the build) and a
test asserts each documented name equals the serialised one, since an
exhaustive match still compiles when only the spellings diverge.

hive-jobq-wire/Cargo.toml

@@ -9,6 +9,10 @@ workspace = true
 
 [dependencies]
 chrono = { workspace = true }
+enumflags2 = { workspace = true }
 hive-jobq = { workspace = true }
 serde = { workspace = true }
 serde_json = { workspace = true }
+# `chrono` for the lifecycle timestamps' schema; the workspace default carries
+# only `axum_extras`, and features are additive so this affects nothing else.
+utoipa = { workspace = true, features = ["chrono"] }